Blasting device



July 24, 1956 D. COURSEN BLASTING DEVICE Filed March 23, 1953 INVENTOR DAVID L. COURSEN ATTORNEY United States Patent 2,755,736 I BLASTING DEVICE David L. Coursen, Newark, DeL, assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., :1 corporation of Delaware Application March 23, 195.3, Serial N 0. 344,130

3 Claims. (Cl. LUZ-25) Th s invent on relates to a reuseabl gas xpa si blasting device. More specifically it is concerned with a gas pansion bla ing device having a flliflblfi pressure build-up section. A

Gas expansion blasting devices are known to the trade. A typical structure is described in U. 8. Patent 2,207,191. It consists essentially of a head section, including firing means, a pressure build-up section adapted to accept a replaceable gas generating charge, and a gas discharge section. In the conventional structure, the head and the discharge venting sections are at opposite ends of the pressure build-up section. The pressure build-up section and discharge section are separated by valving or preferably by a frangible rupture disc. When readied for firing, the apparatus is positioned with its discharge section within a bore hole of suitable diameter. The gas generating composition is then fired. Firing may be accomplished by means of a heating element or a squib to which current is supplied through electrodes. At a predetermined pressure the compressed gas is released, preferably by rupture of a frangible disc. This release of gas occurs with neither spark nor flame.

During the period prior to gas release, it is essential that the pressure build-up section be properly sealed. This may be accomplished by the use of resilient sealing ring packings. Where such packings are a part of the removable head and/or gas discharge section, disassembly of a pressurized unit becomes very hazardous since the pressure build-up section may remain sealed until the threaded portions are so few as to be stripped, causing the parts to separate in a violent fashion. The problem is especially acute where the packing is of a free floating pressureseal type. Structures of the this type are described in copending applications Serial Nos. 274,254 filed February 29, 1952, by F. A. Loving (allowed October 9, 1952), 294,360 filed April 25, 1952, by J. P. Swed (allowed February 3, 1953), and 299,695 filed July 18, 1952, by F. A. Loving. Application Serial No. 274,254 describes a closure assembly for the discharge end wherein a sleeve on the high pressure side of a rupture disc contains a peripheral groove open to the side of the tube body and an annular groove adjacent to the disc, both grooves containing a resilient sealing element, preferably 0 rings. In application Serial No. 284,360, a similar sleeve arrangement is disclosed, except that the annular groove is replaced with an annular ridge of a metal harder than the disc metal. In application Serial No. 299,695, the sealing element is in a peripheral channel located on the discharge head body itself, and thus on the low pressure side of the disc. When any of the foregoing closures are utilized, only hand tightening of the assembly is required, and the seal obtained is highly elfective. A similar seal can also be utilized at the firing-head end of the blasting cartridge with the same success.

It is an object of the present invention to provide a gas expansion blasting device having a ventable pressure build-up section.

Another object is to provide a venting means for a gas expansion blasting device, the pressure build-up section .of which is made gas tight by a floating, pressure-seal packing.

These and other objects will become apparent in the course .of the following specification and claims.

In accordance with the present invention a venting .port is provided immediately adjacent to the 'low pressure side of each sealing element. Thus when disassembly is commenced, the first few turns of the threaded and sealed head and/or gas discharge sections exposes the venting port thereby releasing the gases confined within the pressure build-up section.

The invention is more fully understood by reference to the drawings.

Figure 1 is a fragmentary elevation partly in cross section showing typical sealing arrangements on either end of the pressure build-up section, each with a venting port; and

Figure 2 is a fragmentary elevation partly in cross section showing an alternative typical seal construction, also with a venting port.

Referring to Figure l, the seal between the gas discharge section 1 and the pressure build-up section 2 is provided by a free floating, pressure seal packing consisting of sleeve 3 having resilient ring packing 4 and an annular ridge 5 held tightly against rupture disc 6 by the gas pressure within the pressure build-up section. Upon backing off the gas discharge section, the rupture disc and the free floating, pressure seal packing follow it. When the resilient ring packing passes venting port 7, the pressure is released to the atmosphere. A venting arrangement may also be provided at the threaded joint between the head section 8 and the pressure build-up section. Thus a resilient ring packing 9 on a sleeve extension 10 of the head section will provide a seal until the head section is backed off to the point where it passes venting port 11. In Figure 2, a seal is provided on the low pressure side of rupture disc 12 by means of annular ridge 13 and resilient ring packing 14 until the gas discharge section is backed off sufiiciently to bleed the generat d gases through venting port 15.

The venting port may consist of a single hole drilled through the wall of the pressure build-up section or multiple holes. The size of the holes may vary depending upon their number, the character of the residue material produced by gas generation, the strength of the structure and similar factors. A diameter of inch is sutlicient to avoid clogging by minute particles, particularly the residue within the apparatus after gas generation. A hole as large as /2 inch is satisfactory where the structure is fabricated from high carbon steel having a diameter of about 2 /2 inches. While a venting port at either threaded connection is sufficient to permit bleeding of the apparatus, it is preferred to have such a port at both threaded connections. This is especially true where the gas generating material produces pressure insufficient to actuate the release device, such a condition being commonly referred to as a hot shot. In such a situation disassembly might Well be attempted with no knowledge of the presence of pressure.

It is preferred that the venting port be located immediately adjacent to the low pressure side of the resilient ring packing. However, it is essential only that the high pressure face of the ring be between the venting port and the confined gas. Thus the packing may actually cover the venting port. The maximum permissible distance of the venting port from the low pressure side of the packing will depend upon the length of the threaded section. In any event, the port should be no further from the pressure face of the resilient packing than about three times the cross sectional diameter of the resilient ring.

This normally permits exposure of the venting port within about two turns on disassembly.

The nature and construction of the resilient ring packing is not critical. Any packing'sufficient to confine the pressure is adequate. It is preferred that it be round in cross section. However, at times it may advantageously be square in cross section or be of the expansible V type. Single or multiple rings may be employed in any packing.

The nature of the confined gas is not important to an understanding of the present invention. Furthermore, while the invention is particularly applicable to an apparatus wherein the gas is generated or expanded within its pressure build-up section, it is also adaptable to an apparatus where the gas is pumped in from an external source.

Many equivalent modifications will be obvious from this description to those skilled in the art without a departure from the inventive concept.

What is claimed is:

1. In a blasting device of the type described wherein a tubular pressure chamber is internally threaded for a distance near each end to removably receive an externally threaded firing head section at one end and an externally threaded gas discharge head at the other end and having a resilient sealing member within the chamber beyond but near a threaded portion when the corresponding end section is at its innermost position; an improved safety feature which comprises a passageway through the wall of said chamber having its inner mouth located within that area of the chamber bounded on one side by the position of the sealing member when the nearby end section is at its innermost position and bounded on the other side by the position of that same sealing member when the same end section is partially unthreaded to a point where the remaining threads will still serve to prevent dislodgement of the end section from the tubular chamber by the outward force of pressure in the chamber.

2. A safety feature as claimed in claim 1, wherein said passageway is at right angles to the longitudinal axis of the tube body.

3. A safety feature as claimed in claim 1, wherein said passageway has a diameter of from to /2 inch.

References Cited in the file of this patent UNITED STATES PATENTS 1,818,993 Kneeland Aug. 18, 1931 

1. IN A BLASTING DEVICE OF THE TYPE DESCRIBED WHEREIN A TUBULAR PRESSURE CHAMBER IS INTERNALLY THREADED FOR A DISTANCE NEAR EACH END TO REMOVABLY RECEIVE AN EXTERNALLY THREADED FIRING HEAD SECTION AT ONE END AND AN EXTERNALLY THREADED GAS DISCHARGE HEAD AT THE OTHER END AND HAVING A RESILIENT SEALING MEMBER WITHIN THE CHAMBER BEYOND BUT NEAR A THREADED PORTION WHEN THE CORRESPONDING END SECTION IS AT ITS INNERMOST POSITION; AN IMPROVED SAFTEY FEATURE WHICH COMPRISES A PASSAGEWAY THROUGH THE WALL OF SAID CHAMBER HAVING ITS INNER MOUTH LOCATED WITHIN THAT AREA OF THE CHAMBER BOUNDED ON ONE SIDE BY THE POSITION OF THE SEALING MEMBER WHEN THE NEARBY END SECTION IS AT ITS INNERMOST POSITION AND BOUNDED ON THE OTHER SIDE BY THE POSITION OF THAT SAME SEALING MEMBER WHEN THE SAME END SECTION IS PARTIALLY UNTHREADED TO A POINT WHERE THE REMAINING THREADS WILL STILL SERVE TO PREVENT DISLODGEMENT OF THE END SECTION FROM THE TUBULAR CHAMBER BY THE OUTWARD FORCE OF PRESSURE IN THE CHAMBER. 